H03M13/6508—Flexibility, adaptability, parametrability and configurability of the implementation

Abstract

Method for optimising, under performance constraint, the size of blocks of coded data method of optimising the size of blocks of coded data intended to be subjected to iterative decoding, a maximum error rate at the output of the iterative decoding being fixed in advance, in which there are sought, amongst a plurality of block sizes (N/k) which are submultiples of the normal block size by an integer factor (k) greater than or equal to 1 and a plurality of integers giving the maximum number of iterations (niteration(k)) which can be effected by the said iterative decoding on a block, a submultiple size and a maximum number of iterations such that they are compatible with the said maximum error rate and such that a mean number of iterations n<k>(iteration) which would be effected by the iterative decoding on a block of submultiple size is as low as possible.

Description

The present invention relates to make the size method for optimizing of the coded data block that must carry out iterative decoding, such as the method for in fast decoder (turbodecoder) or fast uniform device (turboequaliser), implementing.This method can be applicable to so-called third generation telecommunication system especially.

Background technology

The notion of speed code (turbocode) is by C.Berrou, A.Glavieux and P.Thitimajshima are at their paper " Near Shannon Limit Error-Correcting Coding and Decoding:Turbo-codes (near the error correction coding and the decoding of shannon limit: speed code) ", ICC-1993, Conference Proceedings, introduce among the pp.1064-1070, just as is known, it has obtained many development.

We remember, fast coding (turbocoding) is to utilize the cascade of the basic code that (interleaving) step that interweaves separates to produce.These basic codes can have different types: be used for the recursive system sign indicating number (being expressed as RSC) of convolution speed code or be used for the piece speed code block code (RS, BCH).The latter is by R.Pyndiah, P.Combelles and P.Adde are " A very low complexity block tubo decoder for product codes (the piece fast decoder that is used for the very low-complexity of product code) " at exercise question, pubeished in Proc.Of IEEE Globecom. describes in the paper of pp.101-105.Imagined dissimilar cascades, such as parallel cascade, identical therein information is encoded dividually by each encoder after being interleaved, and serially concatenated, and wherein the output with each encoder was being interweaved in the past by later encoder encodes.Detailed explanation, for parallel cascade, can be with reference to the article of above-mentioned, Berrou etc., and for serially concatenated, can be with reference to S.Benedetto, G.Montorsi, D.Divsalar, with the article of F.Pollara, " Serialconcatenation of interleaved codes:Performance analysis, design and iterative decoding (serially concatenated of interlaced code: performance evaluation; design and iterative decoding) ", JPL TDA Progr.Rep., Vol.42-126, Aug.1996.

The decoding of speed code is implemented by means of iterative process (being also referred to as fast decoding) traditionally, comprise a series of basic decoded operations, each basic decoded operation receives the input value of weighting and the output valve of weighting is provided, be related to the input of corresponding basic coding operation respectively, and, be related to the output of corresponding basic coding operation for the serial speed code.The representative of the input and output value of these weightings is at the input of corresponding basic encoding unit and the binary system that output (for the serial speed code) is located and the probability of M system.Deinterleave and interlace operation takes place as the function of the interlace operation of carrying out in when coding, and make that each basic decoded operation can be to consider this data with the same order of the input end of respective coding operation.

Fig. 1 a schematically shows the example of speedy coder.Shown speedy coder is the parallel speedy coder of two dimension.Information x with data block form is by first basic encoding unit, 110 codings, so that the first output valve y is provided
1, and after interweaving by interleaver 115, by second basic encoding unit, 120 codings, so that the second output valve y is provided
2System information before being interweaved by channel interleaver 140, in 130 with information encoded y
1And y
2Multiply each other.

Aspect reception, information is deciphered by the fast decoder shown in Fig. 1 b.After in channel deinterleaver 145, deinterleaving, information x, y
1, and y
2By demultiplexer 150 along separate routes.For example, the basic decoder 160 and 170 of Log MAP type corresponds respectively to basic encoding unit 110 and 120.The decoder 160 of weighting input and output type receives prior information and the coded message y of x
1, so that draw the posterior information of x thus.Difference between posterior information and the prior information is called as extrinsic information.Prior information and the extrinsic information e that provides by first decoder with x
1Interweave, addition then is so that be provided to decoder 170 with the new prior information of x (or be x ' more accurately, i.e. the version that interweaves of x).Decoder 170 is from this prior information and coded message y
2The posterior information of valuation x.Therefrom draw intrinsic information e ' by difference in 171
2, afterwards, in deinterleaver 180, deinterleave, in 151, be added on the system information then, so that the new prior information of x is provided to decoder 160.Then these decoding steps are repeated predetermined number n
IterationIteration.The adaptable numerical value of the output of decoder 170 is submitted to judgment device 190, so that the hard decision value is provided.The error correction of the output function to 190 check 195 determines whether decode block are faultless, and under sure situation, interrupts iteration and needn't wait for and arrive predetermined number n
IterationIn addition, in order to determine iteration stopping, fast decoder can not use CRC, and use is about another stopping criterion of weighted value, such as J.Hagenauer's etc., exercise question is " Iterative decoding of binary blockand convolutional codes (iterative decoding of binary block and convolution code) ", IEEETransactions on Information Theory, vol.42, pp.429-445, the article of March1996 or M.Moher's, exercise question is " Decding via cross entropyminimization (by the decoding of entropy minimization) ", Proc.IEEE Globecom Conf., Houston, TX, pp.809-813, the criterion that discloses in the article of Dec.1993.

The former reason C.D of iterative decoding etc. is " Iterative Correction ofIntersymbol Interference:Turbo-equalization (iteration correction of intersymbol interference: fast uniform) " at exercise question, European Trans.Telecomm., vol.6, No.5, Sept./Oct., be replaced by equilibrium in the article of pp.507-511.This iteration equalizing method, be also referred to as fast uniform, from following principle: be subjected to the channel of intersymbol interference (ISI) influence can be considered to be equivalent to convolution coder, therefore, the cascade of channel encoder, interleaver and transmission channel itself can be thought and is equivalent to speedy coder.

Fig. 2 b schematically represents the structure of fast uniform device.Suppose that data are subjected to chnnel coding in encoder 201 in a side identical with the transmitter shown in Fig. 2 a, in interleaver 202, be interleaved afterwards, and in modulator 203, carry out the sign reversing of M system.The form of data with the symbolic blocks that interweaved by channel interleaver 204 sent.This fast uniform device at first comprises channel deinterleaver 210, and the back provides the adaptable numerical value of coded data with Log-MAP type weighting output equalizer is arranged.These data are deinterleaved in deinterleaver 230, are deciphered by the Log-MAP type decoder that has weighting output afterwards.The adaptable numerical value that sends from decoder 240 is submitted to judgment device 250, and corresponding hard decision value is provided.Weighted value at the input end of decoder 240 is deducted from output valve, so that extrinsic information e is provided.After interweaving, this extrinsic information is deducted from the output of equalizer 220 on the one hand, is modulated again on the other hand, is sent to equalizer 220 afterwards.From symbol that receives and the intrinsic information of being modulated again, equalizer 220 carries out new priori estimation.Therefore the fast uniform device carries out the iteration of predetermined number to symbolic blocks.Error correction check 260 diagnosis of the output 250 exist or do not have mistake, and iterative process is interrupted no longer iteration, and needn't wait by the time predetermined number.Shut down criterion in addition and can be related to weighted value, as what see in the above.

About design, should be pointed out that can be in same processor or be aligned in the special circuit of streamline and carry out iteration one by one for fast coding and fast uniform, and each is responsible for the iteration of given order number.

Under the situation of fast coding and fast uniform, the performance of representing with the error rate (BET) or packet error probability (PET) is good more, and the length of the size N of inner interleaver (IL) is big more.This is because the size of inner interleaver increases, and that is to say that the size of the piece that its implementation is interweaved increases, and has improved Hamming (Hamming) weight distribution of speed code and the usefulness of iterative decoding.This gain that interweaves changes with the speed code type.After this, term " performance " will indistinguishably use with the BET or the PET of decoding data.

The gain that interweaves of the speedy coder of Fig. 3 example ground displayed map 1a, when the size N of piece when 200 change to 1000, its basic encoding unit is multinomial (13,15)
OctRSC (recursive system convolution) encoder.

The stand-by period of receiver (be a period of time, at this time end, it is operational with the form of decoding that the data block of reception or symbolic blocks are actually) is the key parameters of application item, and when using low N numerical value, know from the prior art level.

In fact the stand-by period at receiver place can be written as:

Tlatency=Trec+NDd.niterations----------(1)

D wherein
dBe the decoding rate of each iteration, and T
RecBe for the necessary time of data block that obtains with the form that deinterleaves.

The reducing and can reach of stand-by period by the size that reduces piece, however cost is the relative reduction of system effectiveness, as what see on Fig. 3.Based on problem of the present invention is under the condition of degrade performance not, defines the piece size N that may obtain compared with the lower stand-by period of prior art level.

When iterative decoding was handled by fast processor, crucial resource no longer was the stand-by period, calculated spent energy but be used to carry out, and itself also is the operation amount that involves when depending on decoding.

Summary of the invention

The problem to be solved in the present invention is under the condition of degrade performance not, determines to allow the piece size N compared with the lower resource cost of prior art level.

The solution that the present invention provides is to stipulate by the feasible size method for optimizing that will carry out the coded data block of iterative decoding, maximum error rate in the output of iterative decoding is fixed in advance, this method is at a plurality of sizes (approximate number (submultiple) that these piece sizes are normal blocks sizes, integer factor is more than or equal to 1) and provide and can implement search approximate number size and greatest iteration number among a plurality of integers of greatest iteration number purpose of described iterative decoding to a piece, so that they are compatible mutually with described maximum error rate, and make that the average iteration number that the piece of approximate number size is carried out iterative decoding is minimum possible.

Advantageously, for the approximate number size of given factor k and given greatest iteration number, described average iteration number is to be confirmed as by the mean value of iterative decoding for the iteration number of each piece enforcement of a series of inferior pieces of doubly taking measurements according to signal noise ratio, if the piece of approximate number size satisfies predetermined reliability criterion, if or the number of the iteration of piece reaches described given greatest iteration number hereto, then stops to carry out iteration.

Preferably will be stored in the table for the average iteration number of different approximate number sizes, different greatest iteration number and different signal noise ratio, this table is along with the carrying out of iterative decoding can be updated.By will advantageously selecting average iteration number from the interpolation of showing obtainable numerical value.

Described search can be limited to the integer that has greater than the numerical value of predetermined value.

According to an embodiment, before search, determine with maximum predetermined decoding time mutually compatibility, for the greatest iteration number of normal blocks size, search in the middle of described a plurality of about several piece sizes and described a plurality of integer is limited to such numerical value, so that the piece of approximate number size is implemented the average iteration number of iterative decoding less than described greatest iteration number.

The present invention stipulates that by the method for iterative decoding coded data piece these pieces have original dimension, and described method is determined optimical block size and the greatest iteration number relevant with this size by the optimization method that discloses above.To in the digital coding in the piece of original dimension the sub-piece of a series of optimum sizes, series of iterations by iterative decoding, with this a little decoding one by one, if satisfy predetermined reliability criterion, if or the number of iteration reaches the described greatest iteration number relevant with described optimum size, then stop to carry out iteration for sub-piece.

The present invention stipulates that by the method for iterative decoding coded data piece these pieces have original dimension, wherein determine optimical block size and the greatest iteration number relevant with this size by the optimization method that discloses above.With the digital coding of the piece of original dimension is the sub-piece of a series of optimum sizes, by each sub-piece adjoining land being implemented the iteration of iterative decoding, with this a little block decoding, if satisfy predetermined reliability criterion, if or the number of iteration reaches the greatest iteration number relevant with described optimum size, then for the unreal row iteration of sub-piece.

The present invention relates to be used for the equipment of iterative decoding by speedy coder coded data piece, device with the optimization method that is used to implement above defined, described device provides the greatest iteration number of optimical block size and each optimum size piece, and this equipment also comprises the device that is used for the optimical block dimension information is sent to speedy coder.

The present invention also relates to the coding/decoding system, comprise the speedy coder of coded data block and the iterative decoding equipment of above regulation of being used for, be used for decoding by speedy coder coded data piece, and the latter comprises and is used to receive described optimical block dimension information and is used for device according to the size of at least one inner interleaver of information correction of described reception.

The present invention also relates to be used for the equipment of coded data block, this equipment has the device of the optimization method that is used to implement above regulation, described device provides the optimical block size, and this equipment also comprises the device that is used for revising adaptively according to described optimical block size the size of coded data block.

At last, the present invention relates to be used for to utilizing encoder encodes and modulated data block to carry out the equipment of fast uniform, device with the optimization method that is used to implement above defined, described device provides the optimical block size, and described equipment also comprises the device that is used for the optimical block dimension information is sent to encoder.

Description of drawings

By reading following explanation for exemplary embodiment, will more clearly understand above-mentioned feature of the present invention or the like, described explanation provides with respect to accompanying drawing, wherein:

Fig. 1 a schematically shows the example of the known speedy coder of prior art level;

Fig. 1 b schematically shows the example speedy coder coded data, that have the fast decoder of known structure that is used for deciphering by Fig. 1 a;

Fig. 2 a schematically shows the example of the known transmitter of prior art level;

The gain that interweaves of the speed code encoder of Fig. 3 displayed map 1a changes to second size from first size;

Fig. 4 shows for the iteration number of given maximum with when using complete shutdown criterion, the average iteration number of the speed code decoder of Fig. 1 b;

Fig. 5 shows for the histogram that satisfies the complete necessary iteration number of stopping criterion;

Fig. 6 shows because the present invention's advantage that cause, average iteration number;

Fig. 7 shows according to the flow chart first embodiment of the present invention, that determine the method for optimical block size.

Embodiment

Based on the such fact of universal utilization of the present invention: in iterative decoder, for predetermined iteration number n
Iterations, will be called as number will be set, data block can entirely be deciphered before the last iteration of plan.For example, be complete criterion (zero BET that is to say, does not have mistake in piece fully) if iteration is shut down criterion, then average iteration number n
IterationsUsually less than number is set, as what on Fig. 4, see.This figure shows for different n
Iterations, n
IterationsChange according to signal noise ratio.Can see, for given number n
Iterations, average iteration number does not reach this numerical value, when signal noise ratio when being very high, and this this especially situation.In fact nature, does not have complete shutdown criterion: for example test and do not have mistake by CRC, in case and CRC no longer detect mistake, just stop iteration.Relevant n
IterationsWith respect to n
IterationsIn any case it is correct that the conclusion of change always keeps.

Fig. 5 is schematically depicted as the histogram that obtains the necessary iteration number of zero BET (with therefore PET).In fact, owing to can not implement infinite population purpose iteration, see as above, draw thus according to (1), with the size of stand-by period and interleaver iteration number n compatible mutually, setting
IterationsHistogrammic mean value n
∞Corresponding to infinity number is set.For the given number that is provided with, mean value n
IterationsBe taken as the area of the hatching of curve.

Suppose the size N of piece now, thus the size of the inner interleaver of hypothesis speedy coder or fast uniform device, and quilt is divided by nonzero integer k.Stand-by period T
Latency(k)(at the end of this time, the k of the size N/k that a reduces data block is decoded) is represented as then:

T wherein
Rec(k)Be time of reception, at the end of this time, the k of a size N/k data block is operational in receiver, wherein is applicable with the form that interweaves.When not having channel interleaving, this time of reception equals
Nk.Du+&Sigma;i=2k&delta;trec(i),N/ (kD wherein
u) be first the time of reception of size N/k, and δ t
Rec(i)It is the time that receiver must be waited between the ending of the reception of the ending of the decoding of (i-1) piece and (i) piece.Therefore, this provides:
Nk.Du&le;Trec(k)<NDu.On the other hand, when in transmitter, implementing to have M
kThe size M of＞N/k
kChannel interleaving the time, this provides:
:Trec(k)=Mk/Du+&Sigma;i=2N/Mk&delta;rec(i),δ wherein
Rec(i)Be kM in (i-1) group
kStand-by period between the ending of the ending that deinterleaves of/N piece and their decoding of one side and the reception of i group on the other hand.In fact, will get M
kSo=N is T
Rec(i)=M
k/ D
u

n
Iterations(i) be to use predetermined shutdown criterion and during, the iteration number n that the i piece of size N/k is implemented by decoder for the iteration number of given setting
Iterations(k)

n
Iterations(k)It is the average iteration number of on the group of k piece, making.Should be pointed out that n
Iterations(k)Usually the number n that depends on the setting of selecting for the size N/k of piece
Iterations(k)And signal noise ratio.After this, (N/k, n
Iterations(k)) will be used in speed code, act on the piece of size N/k and by means of each piece n at the most
Iterations(k)And it is decoded.

Should be pointed out that at first that usually the size Mk of channel interleaving increases with k and reduces (in a broad sense), so be the decreasing function of k: T
Rec(k+1)≤ T
Rec(k)Whether use channel interleaving.

Should also be noted that shutting down criterion can tolerate predetermined residual BER.As mentioned above, can use and shut down criterion and act on weighting output or output or external information, when reaching predetermined reliability threshold value, can trigger iteration and shut down.Under all situations, shut down the reliability that criterion is related to the data block of decoding, just because of this reason, it is also referred to as reliability criterion.The numerical value that employed shutdown criterion is selected to for all k all is identical.

The present invention is based on such fact: iterative decoding process was restrained before reaching the maximum iteration number that is provided with usually, might find the number n of integer k and setting
Inerations(k), so that average iteration number n
Iterations(k)Be to reach n
Iterations(k)＜n
Iterations(1)So, must T
Latency(k)＜T.

Fig. 6 shows two kinds of comparisons between the situation.Iteration is represented by the horizontal line that extends on the length of piece.If still wrong after iteration, this line is a dotted line, otherwise is solid line.The position of mistake is with playing the fork symbolic representation.The top of figure shows the iterative decoding process to the piece of size N, for the number n that is provided with
Iterations(1)=3 iteration satisfies stand-by period constraints 3N/D
d＜T (for simplicity, supposing not have channel interleaving and time of reception is zero).Iterative process is in the not convergence of the end of the 3rd iteration, and the piece of decoding has residual error.The bottom of this figure shows when the size quilt of the piece situation divided by 10 time.The number n that is provided with
Iterations(10)Be selected as equaling 4.Can see, for most, iterative process before four iteration and even before three iteration, restrain.In this example, have only piece No.8 still wrong at the end of the 4th iteration.For same mistake, therefore from 3N/D
dStand-by period change to 2.6N/D
dStand-by period.

Usually, factor k and iteration number n
Iterations(k)Selection make might be from stand-by period T
Lentacy(1)Change to shorter stand-by period T
Lentacy(k), and satisfy given Performance Constraints condition simultaneously.Then at k and n
Iterations(k)Their numerical value of numerical value intermediate search right, make to obtain the shortest possible stand-by period T
Lentacy(k)The numerical value of the k that is adopted must be enough big, so that carry out the average of stand-by period for k the piece of the size N/k that reduces.

Fig. 7 schematically provide according to the first embodiment of the present invention, under the Performance Constraints condition flow chart of piece size method for optimizing.Inner weaving length and piece size N are used in the transmission that 710 places show.Aspect reception,,, determine greatest iteration number n by means of equation (1) from the valuation 721 of N and maximum latency T at 720 places
Iterations(1)In second step 730, system then table 731 in, select k (k 〉=1 and be the divisor of N) numerical value and with the performance level (level) of needs (BET, PET) (the be related to signal noise ratio) n of compatibility mutually
Iterations(1)According to change example of the present invention, as channel interleaving (so the T that uses fixed dimension
Rec(k)Be constant) time, search is limited to numerical value and the n of numerical value k in advance
Iterations(k), so that n
Iterations(k)＜n
Iterations(1)730, in the middle of selected numerical value, determine to provide the shortest stand-by period T then
Iatency(k)Numerical value to (N/k, n
Iterations(k)).

740, whether the numerical value of the k that test is adopted is greater than the average necessary numerical value k for the stand-by period
MinUnder sure situation, thereby the size N/k of numerical value k and new piece is sent to transmitter by Return Channel.Then, the size of the size of speedy coder adjustment piece and its inner interleaver is to this new numerical value.Under the situation of negating, the optimization procedures termination, and the piece size remains unchanged.

As the alternative of described embodiment, do not carry out test 740, the search of his-and-hers watches 731 is limited to greater than k
MinThe numerical value of k.

Table 731 can be shifted to an earlier date with actual iteration number from the performance that obtains or be produced after incident.It also can be produced in advance or be finished in use in system.The numerical value that does not provide on the table can calculate by interpolation from existing numerical value.

According to the second embodiment of the present invention, the optimized process of the size of piece is implemented at the transmitter place, and system does not have Return Channel between receiver and transmitter.The size of piece is corrected at the transmitter place, and the greatest iteration number of each piece is reduced under receiver is in the constraints of the maximum error rate in the output of obeying iterative decoding as far as possible.Like this, obtain average iteration number, thus the receiver stand-by period of the limit of the maximum possible that obtains being reduced.

Whichever embodiment, when the size N of piece by divided by the factor k time, iterative process can be implemented in two possible modes.

Become example according to first, for each piece of k piece, implement to decipher for the first time iteration, after first iteration, implement to decipher for the second time iteration then for piece with residual error, or the like, use until exhausted until operational resource or the time of distributing to the decoding that is used for k piece.In each process, the piece with remaining mistake is identified by shutting down criterion.Like this, can be sure of that the mode of the time of operational resource and distribution with the best is used, and avoid decoding during a piece " delays " oversize, if k be not enough big with guarantee iteration number enough on average, it can impair later piece.

Under the situation of the example of Fig. 6, this enforcement that becomes example will be as follows:

1. for piece 1 to 10 iteration #1

For piece 1 to 10 iteration #2-＞piece 1,2,5,6,10 is correct

3. for piece 3,4,7,8,9 iteration #3-＞piece 3,4,7,9 is correct

4. for piece 8 iteration #4

Duration T when channel interleaving
Rec(k)=M
k/ D
uBe fixedly the time or when k is very little, it is favourable that this first decoding becomes example.This is because must wait for a period of time M before can deciphering a piece under first kind of situation
k/ D
u, and under second kind of situation, it makes might remedy any average defective.

Become routine according to second, each piece of k=10 piece is sequentially decoded.At maximum n
Iterations(10)=4 o'clock, use the shutdown criterion that each piece is sequentially implemented to decipher iteration, so that on 10 all pieces, average, reach each piece
n&OverBar;iterations(10)=2.6.

Under the situation of the example of Fig. 6, this enforcement that becomes example will be as follows:

1. for piece 1 iteration 1 to 2

2. for piece 2 iteration 1 to 2

3. for piece 3 iteration 1 to 3

4. for piece 4 iteration 1 to 3

5. for piece 5 iteration 1 to 2

6. for piece 6 iteration 1 to 2

7. for piece 7 iteration 1 to 3

8. for piece 8 iteration 1 to n
Iterations(10)=4

9. for piece 9 iteration 1 to 3

10. for piece 10 iteration 1 to 2

When the channel interleaving time T
Rec(k)=M
k/ D
uBe when not fixing or when k is very big, it is favourable that this second decoding becomes example.This is because if time M
k/ D
uBe unfixed, then it can be reduced to corresponding to the numerical value that interweaves to the piece of k '＜k size k/N in succession, and this may be cost with the performance loss.As a result, the stand-by period T that provides by (2) formula
Latency(k)Also reduce.

Must be pointed out that the maximum latency of major concern is an example for the operational resource of implementing iterative decoding up to now.Resource also means the energy that is expended by processor, itself is the function of iteration number.More generally, operational resource will mean and be easy to the additional physical quantity that expended by iterative decoding.

Though being the optimization procedures by the size of fast coding piece under the Performance Constraints condition, description of the invention illustrates, but it similarly also is applied to the size optimization procedures of the piece of fast uniform under the Performance Constraints condition, and this optimization can (first embodiment) or (second embodiment) implementation in transmitter in the fast uniform device.

Claims (8)

1. size method for optimizing that makes coded data block, wherein will carry out iterative decoding to described coded data block, it is characterized in that, maximum error rate in the output of iterative decoding is fixed in advance, described method is a plurality of sizes and provide search approximate number size and greatest iteration number between a plurality of integers of greatest iteration number purpose that can implement described iterative decoding to a piece, so that described approximate number size and greatest iteration number are compatible mutually with described maximum error rate, wherein said a plurality of sizes are normal blocks sizes by the approximate number that removes more than or equal to 1 integer factor k; For a piece size and given greatest iteration number, average iteration number is defined as implementing for each piece among the piece of a series of approximate number sizes the mean value of the iteration number of iterative decoding according to the function of signal noise ratio; If the piece of approximate number size satisfies predetermined reliability criterion, if or hereto the iteration number of piece reach described given greatest iteration number, then stop iteration.

2. according to the optimization method of claim 1, it is characterized in that, will be stored in the table for the described average iteration number of different approximate number sizes, different greatest iteration number and different signal noise ratio.

3. according to the optimization method of claim 2, it is characterized in that this table is updated when iterative decoding continues.

4. according to the optimization method of claim 3, it is characterized in that utilization interpolation of obtainable value from described table obtains described average iteration number.

5. according to the optimization method of one of front claim, it is characterized in that integer factor k is greater than a predetermined value, wherein this predetermined value was enough big for a described last average latency.

6. according to the optimization method of one of claim 1-4, it is characterized in that, before search, determine with predetermined maximum decoding time mutually compatibility, for the greatest iteration number of the piece of normal size; And the search between described a plurality of sizes and described a plurality of integer is limited to such value, so that the piece of approximate number size is implemented the average iteration number of iterative decoding less than described greatest iteration number.

7. method that is used for the iterative decoding of coded data block, these pieces have original dimension, it is characterized in that, and the optimical block size is determined according to the optimization method of one of claim 1-4 with the greatest iteration number utilization relevant with this size; And be the sub-piece of a series of optimum sizes with the digital coding of the piece of original dimension; By the iteration of a series of iterative decoding, with this a little decoding one by one; If satisfy predetermined reliability criterion, if or the number of iteration reach the described greatest iteration number relevant with described optimum size, then the antithetical phrase piece stops iteration.

8. method that is used for the iterative decoding of coded data block, these pieces have original dimension, it is characterized in that, and the optimical block size is determined according to the optimization method of one of claim 1-4 with the greatest iteration number utilization relevant with this size; And be the sub-piece of a series of optimum sizes with the digital coding of the piece of original dimension; By each sub-piece being implemented continuously the iteration of iterative decoding, this a little is deciphered; If satisfy predetermined reliability criterion, if or the number of iteration reach the greatest iteration number relevant, antithetical phrase piece enforcement iteration not then with described optimum size.